Trematode flatworms of the genus Schistosoma are the causative agents of schistosomiasis, a tropical parasitic disease with over 200 million people infected worldwide. Praziquantel (PZQ) is the current drug of choice against schistosomiasis, but the mechanism by which PZQ acts remains poorly defined, even several decades following its discovery. Our laboratory has shown that PZQ is likely interacting with a molecular component of schistosome voltage-gated Ca2+ (Cav) channels, specifically a structurally and functionally atypical Cav channel b subunit. This b subunit subtype has been found to date only in platyhelminths;PZQ is not effective against nematodes, and nematode genomes do not contain this variant Cav channel b subunit. This exploratory R21 proposal describes a high-risk/high-potential payoff project to transfer PZQ sensitivity to nematodes by transforming C. elegans with this variant schistosome Cav channel b subunit. We hypothesize that expression of the variant schistosome b subunit in appropriate C. elegans cell types will result in the formation of nematode Cav channels that are sensitive to PZQ. As such, we will place the schistosome b subunit under the control of several different tissue- and cell-specific C. elegans promoters. We will also use conditional promoters to control expression of the gene. If successful, these experiments will offer further compelling evidence that the schistosome variant b subunit is indeed targeted by PZQ, and will also provide the opportunity to acquire important information about the physiological role played by this unique b subunit. Additionally, development of this transgenic model could pave the way for further experiments (as an R01 project) to obtain details of the mode of action of PZQ, including the identification of interacting factors, by exploiting the far more tractable and powerful C. elegans model system. The specific aims of the project are to: 1. Produce transgenic C. elegans lines expressing the schistosome SmCavbvar Cav channel subunit under the control of various promoters. 2. Test transgenic C. elegans lines expressing bvar for sensitivity to PZQ, either in whole worms or in specific tissues. PUBLIC HEALTH RELEVANCE: Schistosomiasis is a major tropical disease caused by parasitic flatworms called schistosomes. Although there is an effective drug against schistosomiasis, the mechanism by which it works is unclear. By understanding that mechanism, it may be possible to obtain drugs that affect the same molecular target, or molecules that interact with that target. In this project, we are using an innovative approach to define the molecular target of this drug with a future goal of identifying other factors that might interact with this drug target.